>>13798903Injection sites are chosen for a few reasons. There is no guarantee that all of the myocarditis is strictly from direct iv injection because there were not aspirating and there is no way to tell where the injection went. Some real bad cases, where people woke up or died from clots all over the body probably were. Blood vessels exist in muscles and obviously needles do not inject in subcellular structures, nor could the amount of fluid stay in such containment.
The goal of injecting into muscles is to have absorption by the muscle tissue with minimum leakage into smaller blood carriers and ideally none into large vessels. Larger muscle groups are chosen when more amount of fluid is required for the injection. I am not sure what kind of mapping has been done on muscle capillaries to justify indirect pathing to larger blood vessels, but there is some statistical justification as larger amounts of solutions are historically injected into larger muscles. It is possible that it would also be safer to inject smaller amounts in larger muscles than those same amounts in small muscles. Although, all fluid thresholds should be targeted to reduce side effects all together while maintaining medicinal value.
